Our team is trying to decide between purchasing a 3d printer or a small mini-mill. Our budget is approximately $1,000.00. Trying to decide between Prusa i3 mk2 printer or Grizzly G8689 Milling Machine. The plan would be to convert the Mill over to CNC at some point.
We are a rookie team, but have students who have experience in a machine shop (gunsmith) and other students who have used 3D printers. We really aren’t sure which would be the most useful for FRC.
How about a compromise?
Get a cnc, hound to be more useful than a 3d printer in my opinion, and combines the 2 skillsets.
Jim,
I would recommend the mill over the 3D printer. With the right set up you will be able to make durable parts for the robot.
I think you will have a problem with your $1,000 budget though. Getting the mill is a start but you can easily spend another $1,000 on tooling.
We are right down the road from you and we would love to help out any way that we can. I sent you a PM with my contact information.
Please contact me when you can.
IMO a good quality printer is better than a terrible quality mill. The mill can do more stuff, but is not worth the time spent dealing with it when there are so many COTS ways to do the same stuff.
So that’s about a $750 milling machine with shipping and handling but no tools.
If you want to continue with that class of machines you might want to review this page as well:
https://littlemachineshop.com/products/product_category.php?category=1387807683
You’d need end mills.
You’d need toe clamps for the deck.
You’d need an edge finder.
1-2-3 blocks.
Parallels.
That’s the content of the LittleMachineShop milling starter kit:
https://littlemachineshop.com/products/product_view.php?ProductID=1262
That’s another $100 with shipping, handling and tax.
A vise suitable for milling.
Measuring tools.
So you’ll easily be at $1,000 with that mill and tooling.
That being said - the travel of this milling machine and the mechanical stiffness is short and low.
So basically it’s milling machine for light work on small pieces.
But…it could do it pretty quickly with a skilled operator.
If I was going to retrofit a machine like that after the fact for short run parts - I’d consider doing CNC for the X/Y axis only.
This avoids touching off tools and unskilled operators writing G-code that drills into the deck.
On the other hand a Prusa I3 3D printer would be a slow machine to make smallish pieces and they won’t be metal.
To me as an Sieg X2 owner with many retrofits to make it what it is today - I would look for a used machine in good shape with some basic tools. The retrofits I made and got the machine with take time and skill to do.
These are some of the modifications I have on my X2: http://www.hossmachine.info/
The latest run of the Robo3D R1+ is available on Amazon for $400 (was originally $900). It’s a really solid 3D printer, and you really can’t beat that price for the build volume and performance it offers.
Mini-Mills can be useful too, though personally most of the designs my teams have used required longer travel than the average mini-mill can provide. That said, if you can come up with another $65 you could pick up one of these and get both a Mill AND a 3D printer.
Compared to a Mini-Mill you might actually find a CNC Router MORE useful since most FRC applications involve cutting sheets of material rather than milling large blocks of material. I will caution that (from personal experience) the X-Carve isn’t the best in terms of accuracy or precision, especially when cutting aluminum. But if you take the time to calibrate it, turn down the speed, and use multiple passes, you can definitely use it to cut sheets of polycarbonate or thin aluminum (though I wouldn’t recommend trying to cut aluminum gearbox plates with it, due to precision).
I’ve been trying to talk our lead mentor into getting a more professional CNC Router (maybe even something with closed-loop control) which would be able to handle the vast majority of our part fabrication with one machine.
Don’t plan on converting the mill to CNC. It’s a lot of work and money that could of been put elsewhere for what’s usually a sub-par result. Fun project but not an effective use of an FRC team’s resources.
I would purchase a good printer over a mill, because you can get really specific and accurate parts, but if your team mostly does parts by hand and less CAD work, do the mill.
It depends on what you’re trying to accomplish.
If you’re worried about emotional impact & drawing students in, personal preference: I like mills more than printers. In high school, I enjoyed metal cutting and thought the plastic doohickies printed on MakerBot 1.0 were stupid. For sponsors - grant committees and education departments tend to like 3D printers, as they sound like the future. YMMV.
If you’re trying to lay the groundwork for long-term (5+ year) competition success, I’d stay away from both of those purchases and focus on high quality basic tools like a terminal crimper or nice drill press/bandsaw, or put it in savings for an Onyx or used Bridgeport or a cheap CNC router - all gamechanging tools at ~$3-4k.
Maybe the mill, with the knowledge that the mill should be replaced by a full scale knee mill in the future. Don’t bother trying to convert it to CNC, put that effort into a router.
We’ve had a similar desktop mill for five years, have occasionally made single gear reduction plates for manipulators, have milled gussets and brackets from angle or boxbeam, but have never made [2-CIM WCD] gearbox plates on it (always farmed that out to sponsors).
It’s not a nice enough machine to skip the dykem layout step (not enough rigidity). The travel is too small for big manipulator mechanism beams, so we end up unclamping & reclamping on some parts, rendering it equivalent to a drill press and steady hand.
About 80% the time we are using it as a Fancier Drill Press, and a nice drill press would do that job better. About 10% of the time we are using it as a Fancier Bandsaw, and a nice band saw would do that job equally well. The remaining 10% of the time we are cutting slots, and most of the time you can get creative and design out the slot.
Ditto on this; CNC conversions are something best done with access to a manual mill anyway IMO.
The X-carve is not that great of a CNC router from what I’ve seen. The new Shapeoko 3 actually cuts aluminum surprisingly well out of the box (3991 is getting 0.03" DOC at 16ipm using an Onsrud bit) so if you wanted to spring for a cheap router that would be my preference. $1,100 though, so slightly above your budget.
Avoid tiny tabletop mills. For the price of one of those, you can get a used Bridgeport mill. Bridgeports are by far the best manual machines I’ve ever user and are packed chock-full of useful features (most of which you will not use). An auction in CA recently had them going for well under the new price.
I used a manual Bridgeport on 115 for four years with no issues. 3D printing is nice, but when you need the strength of aluminum and precision for gearboxes or belts, you can’t beat a bridgeport for the utility. I cannot imagine having to build robots without a bridgeport or other precision metal-cutting machine.
A quick look at Craiglist in your area shows Bridgeport for around $1,900, which doesn’t include tooling. You may be better off calling any local machine dealers and seeing what they can do for you if you decide you want a mill.
Don’t actually buy the rusted nonsense at $500, stick to $1.5-2k for a working model that just needs to get trammed in and greased.
A quick look at Craiglist in your area shows Bridgeport for around $1,900, which doesn’t include tooling. You may be better off calling any local machine dealers and seeing what they can do for you if you decide you want a mill.
+$1k for tooling = $3k for gamechanging team capability.
Asid61 & I are neglecting 3-phase power, bolting to concrete slab, etc in this estimate, and assuming you have a permanent build space. The Shapeko will travel easily if you’re still in a ‘floating’ stage with less-permanent or non-customizable build space.
Our only mill is the Harbor Freight version of the benchtop Sieg / Grizzly you’re considering.
For robot-building purposes, the mini-mill is excellent for a light-resource team. Your kids will learn precision measurement, setup, workholding, tool selection, feeds & speeds, plus a lot more. They’ll learn to design within their fabrication abilities, and that’s a good thing. The mill is super-portable in the event you want to move it. It runs on 110V. Plug it in and go. Boom. Robot parts.
Our 3D Printer is the Prusa i3. Awesome little tool and we’ve really grown to really like it after a summer of experimentation. Ours was effective in helping students put immediate results behind CAD ideas. It will make good robot parts - as long as you design with a decent understanding of the strength of plastics. I expect we’ll use it for some structural FRC components as we get more miles on it but there’s a pretty significant learning curve until you can put your faith in little strings of melted PLA.
For practicality sake, go for the mill first and make perfectly good parts from aluminum. When the off-season hits, get a 3D-Printer and go nuts with it.
As the others have said, a real Bridgeport is far superior and should be an aspirational purchase if it’s not in the cards this year. But don’t worry about being too limited by a benchtop mill. With some creativity, the gunsmiths will be able to whittle up just about anything with it.
Get it trammed, but please don’t grease it. It needs way oil for the slideways and spindle oil for the spindle. Many Bridgeport and other mills have been messed up by clogging the way lube lines with grease. Also, you should not need to bolt down a Bridgeport. Ours at work in earthquake country were not bolted down. You can get three phase for a 1-hp Bridgeport out of a 120-V 20-A outlet using a VFD for <$150. I helped Team 199 set one up that way.
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I went and ran all three bridgeports at the auction when I went there with the intention of buying a lathe actually. Only one of them had surface rust and it wasn’t on the ways, the lighting is what makes it seem bad. Usually mills outside of CA are even cheaper to boot.
Completely forgot about 3-phase. Many schools have it but your build space may not. Phase converters or VFDs for the usual 2HP Bridgeport motor are typically $100-300 depending on where you buy from.
It’s probably worth just saving the money and trying to raise another $4-5k and buy something used from a reputable source if you’re getting a mill. I know that’s not what you want to hear; but we’ve bought junk early on as a team and now replacing it all.
I like the idea of the x-carve machine or another CNC router option if you’re looking to build up good manufacturing capabilities. But you’re going to have the same problem as with the mill where you need to spend another chunk of money on tools and clamps. We just got our router in August and we think easily 80% or more of our robot is going to built on it. Plus some parts that we may have 3D printed in the past we now make on the router (attached is a Hex bushing we made out of Nylon in about 2 minutes on the router that in prior years we’d have 3D printed).
I think 3D printers are cool; but if you can’t build basic plates/parts out of aluminum nor drill holes with some OK positional tolerance then I think the 3D printer is more of a distraction than help. Although, we have used ours in the past to make drill fixtures/guide templates that we would clamp to aluminum parts and drill out by hand/drill press before we had a mill. But, you could easily just print a 1:1 scale drawing from solid works and spray adhesive it on the part as a reference guide.
Done both, but I think the advantage goes to the 3D printed pieces if either of two conditions exist:
Speaking from experience, I would say that it depends a LOT on your team’s building style and what you think would be more helpful. In my experience, 3D printers can be more versatile, and possibly faster/do stuff that’s nearly impossible with a mill. Problem with that is, the mill can work metal, and the printers have a “print head allowance” that you have to factor in (and you could still be wrong). But when you’re churning out parts, the printer can likely run overnight, with a bunch of different parts, while the mill is idle due to lack of operators.
That being said… I’ll do the typical engineer thing and pick Option 3. Get a benchtop lathe. Good for spacers, intake rollers (and intake belt pulleys), axles, and other similar items. (Unless, of course, you guys already have access to a full-sized one.) My personal hierarchy has that slightly ahead of a manual mill due to the variety of things you can do with a properly-set up lathe.
I’m a bit of a machining and hardware lightweight, what makes a good CNC vs a not so great one?
You should probably go for the mill, look used though, you may be able to find something better for that price.
Not out of the box*. Had to spend a solid day or two completely ripping it apart and re-building it to make it rigid. Out of the box, the z-axis had a lot of wobble resulting in vibrations and was breaking bits left and right at higher speeds. Of course it probably would have been fine at slower speeds, but I just kept wanting to push it.
The basic construction of the X-Carve and Shapeoko 3 are the same, but the main difference is that the Shapeoko 3 incorporates much stiffer rails. The X-Carve is based on the Shapeoko 2 IIRC, which used much smaller rails. The key in buying a CNC router is looking for rigidity. Things like precision linear rails, ballscrews, and weight all affect that.
My bad, I was thinking of the kit version that doesn’t come assembled. Still, no major modifications to get it working with aluminum is a big plus for me.